1. Field of the Invention
Embodiments of the invention generally relate to a metallization process for manufacturing semiconductor devices, and more particularly, to depositing ruthenium and copper materials on a substrate.
2. Description of the Related Art
Copper is the current metal of choice for use in multilevel metallization processes that are crucial to semiconductor and electronic device manufacturing. The multilevel interconnects that drive the manufacturing processes require planarization of high aspect ratio apertures including contacts, vias, lines, and other features. Filling the features without creating voids or deforming the feature geometry is more difficult when the features have higher aspect ratios. Reliable formation of interconnects is also more difficult as manufacturers strive to increase circuit density and quality.
As the use of copper has permeated the marketplace because of its relative low cost and processing properties, semiconductor manufacturers continue to look for ways to improve the boundary regions between copper and dielectric material by reducing copper diffusion and dewetting. Several processing methods have been developed to manufacture copper interconnects as feature sizes have decreased. Each processing method may increase the likelihood of errors such as copper diffusion across boundary regions, copper crystalline structure deformation, and dewetting. Physical vapor deposition (PVD), chemical vapor deposition (CVD), atomic layer deposition (ALD), electrochemical plating (ECP), and electroless deposition, are processes for depositing copper while chemical mechanical polishing (CMP) and electrochemical mechanical polishing (ECMP) are processes for removing copper. These processes utilize mechanical, electrical, and/or chemical techniques to manipulate the copper materials that form interconnects. Barrier and capping layers may be deposited to contain the copper material.
In the past, a layer of tantalum, tantalum nitride, or copper alloy with tin, aluminum, or magnesium was used to provide a barrier layer or an adhesion promoter between copper and other materials. These options are costly or only partially effective or both. As the copper atoms along the boundary regions experience changes in temperature, pressure, atmospheric conditions, or other process variables common during multiple step semiconductor processing, the copper may migrate along the boundary regions and become agglomerated copper. The copper may also be less uniformly dispersed along the boundary regions and become dewetted copper. These changes in the boundary region include stress migration and electromigration of the copper atoms. The stress migration and electromigration of copper across the dielectric layers or other structures increases the resistivity of the resulting structures and reduces the reliability of the resulting devices.
Barrier layers containing ruthenium have been deposited by PVD, CVD, and ALD processes. PVD processes for depositing ruthenium are often hard to control the precise thicknesses of the deposited material. CVD processes usually suffer from poor conformality and contaminants in the deposited ruthenium-containing film. During a typical ALD process, a ruthenium precursor and a reducing agent are sequentially exposed to a substrate to form the desired ruthenium-containing film. ALD processes have several advantages over other vapor deposition processes, such as very conformal films and the ability to deposit into high aspect ratio vias. However, the deposition rates of an ALD process are often too slow, so that ALD processes are not often used in commercial applications. Also, ruthenium is usually deposited across the overall substrate surface by ALD, regardless that the exposed substrate surface may have various types of materials.
Therefore, a need exists to enhance the stability and adhesion of copper-containing layers, especially for copper seed layers. Also, a need exists to improve the electromigration (EM) reliability of copper-containing layer, especially for copper line formations, while preventing the diffusion of copper into neighboring materials, such as dielectric materials. A further need exists for an improved vapor deposition process to deposit ruthenium materials.